Hi Lukas,
Thanks so much for your report!
You’re talking about the custom CSS of an element in which you use classes, right?
A page/template revision in Bricks follows the same principle as normal WP post revisions: it is a collection of snapshots of the page’s elements data, with each snapshot generated on builder save.
Classes are not specific to a page, so they are not part of the page revision, just as theme styles or color palettes are not part of revisions.
Best regards,
timmse